Enabling data integrity checking and faster application recovery in synchronous replicated datasets

ABSTRACT

One or more techniques and/or computing devices are provided for utilizing snapshots for data integrity validation and/or faster application recovery. For example, a first storage controller, hosting first storage, has a synchronous replication relationship with a second storage controller hosting second storage. A snapshot replication policy rule is defined to specify that a replication label is to be used for snapshot create requests, targeting the first storage, that are to be replicated to the second storage. A snapshot creation policy is created to issue snapshot create requests comprising the replication label. Thus a snapshot of the first storage and a replication snapshot of the second storage are created based upon a snapshot create request comprising the replication label. The snapshot and the replication snapshot may be compared for data integrity validation (e.g., determine whether the snapshots comprise the same data) and/or quickly recovering an application after a disaster.

RELATED APPLICATIONS

This application claims priority to and is a continuation of U.S.application Ser. No. 16/730,832, filed on Dec. 30, 2019, now allowed,titled “ENABLING DATA INTEGRITY CHECKING AND FASTER APPLICATION RECOVERYIN SYNCHRONOUS REPLICATED DATASET,” which claims priority to and is acontinuation of U.S. Pat. No. 10,552,064, filed on Feb. 1, 2019 andtitled “ENABLING DATA INTEGRITY CHECKING AND FASTER APPLICATION RECOVERYIN SYNCHRONOUS REPLICATED DATASET,” which claims priority to and is acontinuation of U.S. Pat. No. 10,228,871, filed on Feb. 22, 2016 andtitled “ENABLING DATA INTEGRITY CHECKING AND FASTER APPLICATION RECOVERYIN SYNCHRONOUS REPLICATED DATASETS,” which are incorporated herein byreference.

BACKGROUND

Many storage networks may implement data replication and/or otherredundancy data access techniques for data loss protection andnon-disruptive client access. For example, a first storage cluster maycomprise a first storage controller configured to provide clients withprimary access to data stored within a first storage device and/or otherstorage devices. A second storage cluster may comprise a second storagecontroller configured to provide clients with primary access to datastored within a second storage device and/or other storage devices. Thefirst storage controller and the second storage controller may beconfigured according to a disaster recovery relationship, such that thesecond storage controller may provide failover access to replicated datathat was replicated from the first storage device to a secondary storagedevice, owned by the first storage controller, but accessible to thesecond storage controller (e.g., a switchover operation may be performedwhere the second storage controller assumes ownership of the secondarystorage device and/or other storage devices previously owned by thefirst storage controller so that the second storage controller mayprovide clients with failover access to replicated data within suchstorage devices). In an example of a logical replication scheme, thesecond storage controller has ownership of the replicated data. Thesecond storage controller may provide read-only access to the replicateddata. The second storage controller may convert the replicated data tofull read-write access upon failover. In an example of physicalreplication, the storage device, comprising the replicated data, isowned by the first storage controller until a failover/switchover to thesecond storage controller occurs.

In an example, the second storage cluster may be located at a remotesite to the first storage cluster (e.g., storage clusters may be locatedin different buildings, cities, thousands of kilometers from oneanother, etc.). Thus, if a disaster occurs at a site of a storagecluster, then a surviving storage cluster may remain unaffected by thedisaster (e.g., a power outage of a building hosting the first storagecluster may not affect a second building hosting the second storagecluster in a different city).

In an example, two storage controllers within a storage cluster may beconfigured according to a high availability configuration, such as wherethe two storage controllers are locally connected to one another and/orto the same storage devices. In this way, when a storage controllerfails, then a high availability partner storage controller can quicklytakeover for the failed storage controller due to the localconnectivity. Thus, the high availability partner storage controller mayprovide clients with access to data previously accessible through thefailed storage controller.

In an example of a high availability configuration, high availability todata may be provided without using shared storage. In particular, highavailability to data is provided using a synchronous replicated copy ofa primary storage object. The high availability to data may be providedthrough a software defined architecture, using synchronous replication,and is not limited to merely two storage controllers.

Various replication and synchronization techniques may be used toreplicate data (e.g., client data), configuration data (e.g., a size ofa volume, a name of a volume, logical unit number (LUN) configurationdata, etc.), and/or write caching data (e.g., cached write operationsnot yet flushed to a storage device, but cached within memory such as anon-volatile random access memory (NVRAM)) between storage controllersand/or storage devices. Synchronous replication may be used where anincoming write operation to the first storage controller is locallyimplemented upon a first storage object (e.g., a file, a LUN, a LUNspanning multiple volumes, a consistency group of files and/or LUNs, adirectory, a volume, or any other type of object) by the first storagecontroller and remotely implemented upon a second storage object (e.g.,maintained as a fully synchronized copy of the first storage object) bythe second storage controller before an acknowledgement is provided backto a client that sent the incoming write operation. In another example,asynchronous replication may be achieved by capturing snapshots of avolume, determining data differences (e.g., deltas) between a currentsnapshot and a last snapshot used to replicate data to the secondstorage object, and using incremental transfers to send the datadifferences to the second storage controller for implementation upon thesecond storage object. Semi-synchronous replication may be achievedwhere an acknowledgment back to a client for a write request is basedupon local implementation upon the first storage object, but is notdependent upon remote implementation upon the second storage object.

Data integrity validation, corresponding to whether data is beingcorrectly replicated in a synchronous manner while preserving a writeorder consistency (e.g., if a write operation A depends upon completionof a write operation B, then a replicated write operation B should beimplemented by the second storage controller before a replicated writeoperation A), and/or fast application recovery after a disaster (e.g.,how quickly a database application can recover at the second storagecontroller during failover operation after the first storage controller,previously hosting data of the database application, fails or has aplanned shutdown) may rely upon consistent point in time representationsof the first storage object and the second storage object, such assnapshots. However, in-sync synchronous replication does not create orrely upon crash consistent snapshots for updating the second storageobject (e.g., the mirrored storage object), and instead relies upon awrite splitter to update the second storage object, and thus suchconsistent point in time snapshots may not be available for dataintegrity validation and fast application recovery for storagecontrollers with a synchronous replication relationship.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a component block diagram illustrating an example clusterednetwork in accordance with one or more of the provisions set forthherein.

FIG. 2 is a component block diagram illustrating an example data storagesystem in accordance with one or more of the provisions set forthherein.

FIG. 3 is a flow chart illustrating an exemplary method of utilizingsnapshots for data integrity validation and/or application recovery.

FIG. 4A is a component block diagram illustrating an exemplary computingdevice for utilizing snapshots for data integrity validation, where asnapshot replication policy rule is defined and a snapshot creationpolicy is created.

FIG. 4B is a component block diagram illustrating an exemplary computingdevice for utilizing snapshots for data integrity validation, where asnapshot of first storage and a replication snapshot of second storageis created.

FIG. 4C is a component block diagram illustrating an exemplary computingdevice for utilizing snapshots for data integrity validation.

FIG. 5A is a component block diagram illustrating an exemplary computingdevice for utilizing snapshots for application recovery, where asnapshot replication policy rule is defined.

FIG. 5B is a component block diagram illustrating an exemplary computingdevice for utilizing snapshots for application recovery, where asnapshot of first storage and a replication snapshot of second storageis created.

FIG. 5C is a component block diagram illustrating an exemplary computingdevice for utilizing snapshots for application recovery.

FIG. 6 is an example of a computer readable medium in accordance withone or more of the provisions set forth herein.

DETAILED DESCRIPTION

Some examples of the claimed subject matter are now described withreference to the drawings, where like reference numerals are generallyused to refer to like elements throughout. In the following description,for purposes of explanation, numerous specific details are set forth inorder to provide an understanding of the claimed subject matter. It maybe evident, however, that the claimed subject matter may be practicedwithout these specific details. Nothing in this detailed description isadmitted as prior art.

One or more techniques and/or computing devices for utilizing snapshotsfor data integrity validation and/or application recovery are providedherein. For example, a first storage controller, hosting first storage,may have a synchronous replication relationship with a second storagecontroller hosting second storage, such that an operation targeting thefirst storage may be replicated to the second storage before theoperation is acknowledged back to a client. The synchronous replicationrelationship may be specified for any level of granularity of data, suchas for a file, a logical unit number (LUN), a consistency group of filesand/or LUNs, a directory, a volume, and/or any other storage object.Data integrity validation and/or efficient application recovery mayleverage consistent point in time representations of the first storageand the second storage, such as snapshots. However, synchronousreplication splits operations, targeting the first storage, intoreplication operations to target the second storage, as opposed tocreating and using snapshots. Accordingly, as provided herein, snapshotcreate requests, targeting the first storage, are replicated to thesecond storage controller to create replication snapshots of the secondstorage as consistent points in time. Such snapshots may be compared fordata integrity validation to verify that synchronous replication isaccurately replicating data to the second storage while maintaining awrite order dependency. Also, snapshots, created with applicationintegrity and thereby capturing application consistent point-in-timestates, may be used to quickly recover an application. In this way,crash consistent snapshots may be periodically created by a snapshotcreation policy defined on a storage device for data integrity checking.Data integrity checking may utilize any common snapshot and may not relyupon application integration. Application consistent snapshots may becreated (e.g., by an application aware plugin at application consistenttimes) for data integrity checking and faster application recovery.

To provide context for utilizing snapshots for data integrity validationand/or application recovery, FIG. 1 illustrates an embodiment of aclustered network environment 100 or a network storage environment. Itmay be appreciated, however, that the techniques, etc. described hereinmay be implemented within the clustered network environment 100, anon-cluster network environment, and/or a variety of other computingenvironments, such as a desktop computing environment. That is, theinstant disclosure, including the scope of the appended claims, is notmeant to be limited to the examples provided herein. It will beappreciated that where the same or similar components, elements,features, items, modules, etc. are illustrated in later figures but werepreviously discussed with regard to prior figures, that a similar (e.g.,redundant) discussion of the same may be omitted when describing thesubsequent figures (e.g., for purposes of simplicity and ease ofunderstanding).

FIG. 1 is a block diagram illustrating the clustered network environment100 that may implement at least some embodiments of the techniquesand/or systems described herein. The clustered network environment 100comprises data storage systems 102 and 104 that are coupled over acluster fabric 106, such as a computing network embodied as a privateInfiniband, Fibre Channel (FC), or Ethernet network facilitatingcommunication between the data storage systems 102 and 104 (and one ormore modules, component, etc. therein, such as, nodes 116 and 118, forexample). It will be appreciated that while two data storage systems 102and 104 and two nodes 116 and 118 are illustrated in FIG. 1 , that anysuitable number of such components is contemplated. In an example, nodes116, 118 comprise storage controllers (e.g., node 116 may comprise aprimary or local storage controller and node 118 may comprise asecondary or remote storage controller) that provide client devices,such as host devices 108, 110, with access to data stored within datastorage devices 128, 130. Similarly, unless specifically providedotherwise herein, the same is true for other modules, elements,features, items, etc. referenced herein and/or illustrated in theaccompanying drawings. That is, a particular number of components,modules, elements, features, items, etc. disclosed herein is not meantto be interpreted in a limiting manner.

It will be further appreciated that clustered networks are not limitedto any particular geographic areas and can be clustered locally and/orremotely. Thus, in one embodiment a clustered network can be distributedover a plurality of storage systems and/or nodes located in a pluralityof geographic locations; while in another embodiment a clustered networkcan include data storage systems (e.g., 102, 104) residing in a samegeographic location (e.g., in a single onsite rack of data storagedevices).

In the illustrated example, one or more host devices 108, 110 which maycomprise, for example, client devices, personal computers (PCs),computing devices used for storage (e.g., storage servers), and othercomputers or peripheral devices (e.g., printers), are coupled to therespective data storage systems 102, 104 by storage network connections112, 114. Network connection may comprise a local area network (LAN) orwide area network (WAN), for example, that utilizes Network AttachedStorage (NAS) protocols, such as a Common Internet File System (CIFS)protocol or a Network File System (NFS) protocol to exchange datapackets, a Storage Area Network (SAN) protocol, such as Small ComputerSystem Interface (SCSI) or Fiber Channel Protocol (FCP), an objectprotocol, such as S3, etc. Illustratively, the host devices 108, 110 maybe general-purpose computers running applications, and may interact withthe data storage systems 102, 104 using a client/server model forexchange of information. That is, the host device may request data fromthe data storage system (e.g., data on a storage device managed by anetwork storage control configured to process I/O commands issued by thehost device for the storage device), and the data storage system mayreturn results of the request to the host device via one or more storagenetwork connections 112, 114.

The nodes 116, 118 on clustered data storage systems 102, 104 cancomprise network or host nodes that are interconnected as a cluster toprovide data storage and management services, such as to an enterprisehaving remote locations, cloud storage (e.g., a storage endpoint may bestored within a data cloud), etc., for example. Such a node in theclustered network environment 100 can be a device attached to thenetwork as a connection point, redistribution point or communicationendpoint, for example. A node may be capable of sending, receiving,and/or forwarding information over a network communications channel, andcould comprise any device that meets any or all of these criteria. Oneexample of a node may be a data storage and management server attachedto a network, where the server can comprise a general purpose computeror a computing device particularly configured to operate as a server ina data storage and management system.

In an example, a first cluster of nodes such as the nodes 116, 118(e.g., a first set of storage controllers configured to provide accessto a first storage aggregate comprising a first logical grouping of oneor more storage devices) may be located on a first storage site. Asecond cluster of nodes, not illustrated, may be located at a secondstorage site (e.g., a second set of storage controllers configured toprovide access to a second storage aggregate comprising a second logicalgrouping of one or more storage devices). The first cluster of nodes andthe second cluster of nodes may be configured according to a disasterrecovery configuration where a surviving cluster of nodes providesfailover access to storage devices of a disaster cluster of nodes in theevent a disaster occurs at a disaster storage site comprising thedisaster cluster of nodes (e.g., the first cluster of nodes providesclient devices with failover data access to storage devices of thesecond storage aggregate in the event a disaster occurs at the secondstorage site).

As illustrated in the clustered network environment 100, nodes 116, 118can comprise various functional components that coordinate to providedistributed storage architecture for the cluster. For example, the nodescan comprise network modules 120, 122 and data modules 124, 126. Networkmoduless 120, 122 can be configured to allow the nodes 116, 118 (e.g.,network storage controllers) to connect with host devices 108, 110 overthe storage network connections 112, 114, for example, allowing the hostdevices 108, 110 to access data stored in the distributed storagesystem. Further, the network modules 120, 122 can provide connectionswith one or more other components through the cluster fabric 106. Forexample, in FIG. 1 , the network module 120 of node 116 can access asecond data storage device 130 by sending a request through the datamodule 126 of a second node 118.

Data modules 124, 126 can be configured to connect one or more datastorage devices 128, 130, such as disks or arrays of disks, flashmemory, or some other form of data storage, to the nodes 116, 118. Thenodes 116, 118 can be interconnected by the cluster fabric 106, forexample, allowing respective nodes in the cluster to access data on datastorage devices 128, 130 connected to different nodes in the cluster.Often, data modules 124, 126 communicate with the data storage devices128, 130 according to the SAN protocol, such as SCSI or FCP, forexample. Thus, as seen from an operating system on nodes 116, 118, thedata storage devices 128, 130 can appear as locally attached to theoperating system. In this manner, different nodes 116, 118, etc. mayaccess data blocks through the operating system, rather than expresslyrequesting abstract files.

It should be appreciated that, while the clustered network environment100 illustrates an equal number of network and data modules, otherembodiments may comprise a differing number of these modules. Forexample, there may be a plurality of network and data modulesinterconnected in a cluster that does not have a one-to-onecorrespondence between the network and data modules. That is, differentnodes can have a different number of network and data modules, and thesame node can have a different number of network modules than datamodules.

Further, a host device 108, 110 can be networked with the nodes 116, 118in the cluster, over the storage networking connections 112, 114. As anexample, respective host devices 108, 110 that are networked to acluster may request services (e.g., exchanging of information in theform of data packets) of nodes 116, 118 in the cluster, and the nodes116, 118 can return results of the requested services to the hostdevices 108, 110. In one embodiment, the host devices 108, 110 canexchange information with the network modules 120, 122 residing in thenodes 116, 118 (e.g., network hosts) in the data storage systems 102,104.

In one embodiment, the data storage devices 128, 130 comprise volumes132, which is an implementation of storage of information onto diskdrives or disk arrays or other storage (e.g., flash) as a file-systemfor data, for example. Volumes can span a portion of a disk, acollection of disks, or portions of disks, for example, and typicallydefine an overall logical arrangement of file storage on disk space inthe storage system. In one embodiment a volume can comprise stored dataas one or more files that reside in a hierarchical directory structurewithin the volume.

Volumes are typically configured in formats that may be associated withparticular storage systems, and respective volume formats typicallycomprise features that provide functionality to the volumes, such asproviding an ability for volumes to form clusters. For example, where afirst storage system may utilize a first format for their volumes, asecond storage system may utilize a second format for their volumes.

In the clustered network environment 100, the host devices 108, 110 canutilize the data storage systems 102, 104 to store and retrieve datafrom the volumes 132. In this embodiment, for example, the host device108 can send data packets to the network module 120 in the node 116within data storage system 102. The node 116 can forward the data to thedata storage device 128 using the data module 124, where the datastorage device 128 comprises volume 132A. In this way, in this example,the host device can access the volume 132A, to store and/or retrievedata, using the data storage system 102 connected by the networkconnection 112. Further, in this embodiment, the host device 110 canexchange data with the network module 122 in the host 118 within thedata storage system 104 (e.g., which may be remote from the data storagesystem 102). The host 118 can forward the data to the data storagedevice 130 using the data module 126, thereby accessing volume 1328associated with the data storage device 130.

It may be appreciated that utilizing snapshots for data integrityvalidation and/or application recovery may be implemented within theclustered network environment 100. In an example, a snapshot of thevolume 132A, maintained by the node 116 (e.g., a first storagecontroller), and a replication snapshot of the volume 1328, maintainedby the node 118 (e.g., a second storage controller), may be created. Thesnapshots may be compared for data integrity validation and/orapplication recovery. It may be appreciated that utilizing snapshots fordata integrity validation and/or application recovery may be implementedfor and/or between any type of computing environment, and may betransferrable between physical devices (e.g., node 116, node 118, adesktop computer, a tablet, a laptop, a wearable device, a mobiledevice, a storage device, a server, etc.) and/or a cloud computingenvironment (e.g., remote to the clustered network environment 100).

FIG. 2 is an illustrative example of a data storage system 200 (e.g.,102, 104 in FIG. 1 ), providing further detail of an embodiment ofcomponents that may implement one or more of the techniques and/orsystems described herein. The data storage system 200 comprises a node202 (e.g., host nodes 116, 118 in FIG. 1 ), and a data storage device234 (e.g., data storage devices 128, 130 in FIG. 1 ). The node 202 maybe a general purpose computer, for example, or some other computingdevice particularly configured to operate as a storage server. A hostdevice 205 (e.g., 108, 110 in FIG. 1 ) can be connected to the node 202over a network 216, for example, to provides access to files and/orother data stored on the data storage device 234. In an example, thenode 202 comprises a storage controller that provides client devices,such as the host device 205, with access to data stored within datastorage device 234.

The data storage device 234 can comprise mass storage devices, such asdisks 224, 226, 228 of a disk array 218, 220, 222. It will beappreciated that the techniques and systems, described herein, are notlimited by the example embodiment. For example, disks 224, 226, 228 maycomprise any type of mass storage devices, including but not limited tomagnetic disk drives, flash memory, and any other similar media adaptedto store information, including, for example, data (D) and/or parity (P)information.

The node 202 comprises one or more processors 204, a memory 206, anetwork adapter 210, a cluster access adapter 212, and a storage adapter214 interconnected by a system bus 242. The data storage system 200 alsoincludes an operating system 208 installed in the memory 206 of the node202 that can, for example, implement a Redundant Array of Independent(or Inexpensive) Disks (RAID) optimization technique to optimize areconstruction process of data of a failed disk in an array.

The operating system 208 can also manage communications for the datastorage system, and communications between other data storage systemsthat may be in a clustered network, such as attached to a cluster fabric215 (e.g., 106 in FIG. 1 ). Thus, the node 202, such as a networkstorage controller, can respond to host device requests to manage dataon the data storage device 234 (e.g., or additional clustered devices)in accordance with these host device requests. The operating system 208can often establish one or more file systems on the data storage system200, where a file system can include software code and data structuresthat implement a persistent hierarchical namespace of files anddirectories, for example. As an example, when a new data storage device(not shown) is added to a clustered network system, the operating system208 is informed where, in an existing directory tree, new filesassociated with the new data storage device are to be stored. This isoften referred to as “mounting” a file system.

In the example data storage system 200, memory 206 can include storagelocations that are addressable by the processors 204 and networkadapters 210, 212, 214 for storing related software application code anddata structures. The processors 204 and network adapters 210, 212, 214may, for example, include processing elements and/or logic circuitryconfigured to execute the software code and manipulate the datastructures. The operating system 208, portions of which are typicallyresident in the memory 206 and executed by the processing elements,functionally organizes the storage system by, among other things,invoking storage operations in support of a file service implemented bythe storage system. It will be apparent to those skilled in the art thatother processing and memory mechanisms, including various computerreadable media, may be used for storing and/or executing applicationinstructions pertaining to the techniques described herein. For example,the operating system can also utilize one or more control files (notshown) to aid in the provisioning of virtual machines.

The network adapter 210 includes the mechanical, electrical andsignaling circuitry needed to connect the data storage system 200 to ahost device 205 over a network 216, which may comprise, among otherthings, a point-to-point connection or a shared medium, such as a localarea network. The host device 205 (e.g., 108, 110 of FIG. 1 ) may be ageneral-purpose computer configured to execute applications. Asdescribed above, the host device 205 may interact with the data storagesystem 200 in accordance with a client/host model of informationdelivery.

The storage adapter 214 cooperates with the operating system 208executing on the node 202 to access information requested by the hostdevice 205 (e.g., access data on a storage device managed by a networkstorage controller). The information may be stored on any type ofattached array of writeable media such as magnetic disk drives, flashmemory, and/or any other similar media adapted to store information. Inthe example data storage system 200, the information can be stored indata blocks on the disks 224, 226, 228. The storage adapter 214 caninclude input/output (I/O) interface circuitry that couples to the disksover an I/O interconnect arrangement, such as a storage area network(SAN) protocol (e.g., Small Computer System Interface (SCSI), iSCSI,hyperSCSI, Fiber Channel Protocol (FCP)). The information is retrievedby the storage adapter 214 and, if necessary, processed by the one ormore processors 204 (or the storage adapter 214 itself) prior to beingforwarded over the system bus 242 to the network adapter 210 (and/or thecluster access adapter 212 if sending to another node in the cluster)where the information is formatted into a data packet and returned tothe host device 205 over the network 216 (and/or returned to anothernode attached to the cluster over the cluster fabric 215).

In one embodiment, storage of information on disk arrays 218, 220, 222can be implemented as one or more storage volumes 230, 232 that arecomprised of a cluster of disks 224, 226, 228 defining an overalllogical arrangement of disk space. The disks 224, 226, 228 that compriseone or more volumes are typically organized as one or more groups ofRAIDs. As an example, volume 230 comprises an aggregate of disk arrays218 and 220, which comprise the cluster of disks 224 and 226.

In one embodiment, to facilitate access to disks 224, 226, 228, theoperating system 208 may implement a file system (e.g., write anywherefile system) that logically organizes the information as a hierarchicalstructure of directories and files on the disks. In this embodiment,respective files may be implemented as a set of disk blocks configuredto store information, whereas directories may be implemented asspecially formatted files in which information about other files anddirectories are stored.

Whatever the underlying physical configuration within this data storagesystem 200, data can be stored as files within physical and/or virtualvolumes, which can be associated with respective volume identifiers,such as file system identifiers (FSIDs), which can be 32-bits in lengthin one example.

A physical volume corresponds to at least a portion of physical storagedevices whose address, addressable space, location, etc. doesn't change,such as at least some of one or more data storage devices 234 (e.g., aRedundant Array of Independent (or Inexpensive) Disks (RAID system)).Typically the location of the physical volume doesn't change in that the(range of) address(es) used to access it generally remains constant.

A virtual volume, in contrast, is stored over an aggregate of disparateportions of different physical storage devices. The virtual volume maybe a collection of different available portions of different physicalstorage device locations, such as some available space from each of thedisks 224, 226, and/or 228. It will be appreciated that since a virtualvolume is not “tied” to any one particular storage device, a virtualvolume can be said to include a layer of abstraction or virtualization,which allows it to be resized and/or flexible in some regards.

Further, a virtual volume can include one or more logical unit numbers(LUNs) 238, directories 236, Qtrees 235, and files 240. Among otherthings, these features, but more particularly LUNS, allow the disparatememory locations within which data is stored to be identified, forexample, and grouped as data storage unit. As such, the LUNs 238 may becharacterized as constituting a virtual disk or drive upon which datawithin the virtual volume is stored within the aggregate. For example,LUNs are often referred to as virtual drives, such that they emulate ahard drive from a general purpose computer, while they actually comprisedata blocks stored in various parts of a volume.

In one embodiment, one or more data storage devices 234 can have one ormore physical ports, wherein each physical port can be assigned a targetaddress (e.g., SCSI target address). To represent respective volumesstored on a data storage device, a target address on the data storagedevice can be used to identify one or more LUNs 238. Thus, for example,when the node 202 connects to a volume 230, 232 through the storageadapter 214, a connection between the node 202 and the one or more LUNs238 underlying the volume is created.

In one embodiment, respective target addresses can identify multipleLUNs, such that a target address can represent multiple volumes. The I/Ointerface, which can be implemented as circuitry and/or software in thestorage adapter 214 or as executable code residing in memory 206 andexecuted by the processors 204, for example, can connect to volume 230by using one or more addresses that identify the one or more LUNs 238.

It may be appreciated that utilizing snapshots for data integrityvalidation and/or application recovery may be implemented for the datastorage system 200. In an example, a snapshot of the volume 230,maintained by the node 202 (e.g., a first storage controller), and areplication snapshot of a second volume, maintained by a second node(e.g., a second storage controller), may be created. The snapshots maybe compared for data integrity validation and/or application recovery.It may be appreciated that utilizing snapshots for data integrityvalidation and/or application recovery may be implemented for and/orbetween any type of computing environment, and may be transferrablebetween physical devices (e.g., node 202, host device 205, a desktopcomputer, a tablet, a laptop, a wearable device, a mobile device, astorage device, a server, etc.) and/or a cloud computing environment(e.g., remote to the node 202 and/or the host device 205).

One embodiment of utilizing snapshots for data integrity validationand/or application recovery is illustrated by an exemplary method 300 ofFIG. 3 . A first storage controller may host first storage within whicha client may store data. The first storage controller may have asynchronous replication relationship with a second storage controller(e.g., hosted within the same storage site as the first storagecontroller or hosted within a remote storage site such as a differentbuilding, city, or location than the first storage controller), suchthat data is replicated from the first storage to second storageaccessible to the second storage controller. For example, while thesynchronous replication relationship is in-sync, an incoming operation(e.g., a client write operation to modify the first storage) may belocally implemented upon the first storage and replicated to the secondstorage controller for remote implementation upon the second storagebefore the incoming operation is acknowledged back to a client. Thesynchronous replication relationship may be defined for a file, a LUN, aconsistency group of files and/or LUNs, a directory, a volume, and/orany other storage object. The second storage controller may beconfigured as a disaster recovery partner for the first storagecontroller, such that if the first storage controller fails, then thesecond storage controller may provide clients with failover access toreplicated data (e.g., data replicated from the first storage to thesecond storage whose ownership can be taken over by the second storagecontroller) previously accessible through the failed first storagecontroller.

In an example of synchronous replication, an operation, targeting astorage object within the first storage, may be received from a client(e.g., a client write operation to modify a file, a LUN, a consistencygroup, a directory, or any other storage object specified by thesynchronous replication relationship). Responsive to determining thatthe synchronous replication relationship applies to the storage object,the operation may be split into a replication operation. The operationmay be locally implemented upon the storage object. The replicationoperation may be sent to the second storage controller for remoteimplementation upon a replicated storage object within the secondstorage. The replicated storage object corresponds to a mirror/replicaof the storage object. Responsive to the operation and the replicationoperation completing, an acknowledgement may be provided back to theclient.

At 302, a snapshot replication policy rule may be defined for thesynchronous replication relationship. The snapshot replication policyrule may specify that a replication label (e.g., a string, such as “myvalidation snapshots”, not commonly used for snapshots) will be used forsnapshot create requests, targeting the first storage, that are to bereplicated to the second storage. The snapshot replication policy rule(e.g., a rule within a snapshot replication policy corresponding to aconfiguration for a synchronous replication data path) may be attachedto the synchronous replication relationship.

At 304, a snapshot creation policy, to issue snapshot create requestscomprising the replication label, may be created. In an example, thesnapshot creation policy may be attached to the first storage (e.g.,attached to a volume). For example, the snapshot creation policy maycomprise a schedule parameter for a snapshot policy to create snapshotcreate requests with the replication label.

In an example, a replication mechanism (e.g., an application consistentsnapshot (ACS) replication mechanism) may receive a snapshot createrequest. The replication mechanism may evaluate the snapshot createrequest to determine whether the snapshot create request comprises thereplication label specified within the snapshot replication policy rule.Responsive to the snapshot create request not comprising the replicationlabel, a snapshot of the first storage at the first storage controllermay be created without creating a corresponding replication snapshot ofthe second storage at the second storage controller.

Responsive to the snapshot create request comprising the replicationlabel, a snapshot of the first storage may be created at the firststorage controller, at 306. At 308, the snapshot create request may bereplicated to the second storage controller based upon the snapshotcreate request comprising the replication label, such that a replicationsnapshot of the second storage is created at the second storagecontroller. In this way, the snapshot and the replication snapshotshould be consistent point in time representations of the first andsecond storage, and thus may be evaluated to determine whethersynchronous replication is being performed correctly.

At 310, the snapshot and the replication snapshot may be compared fordata integrity validation (e.g., compared to determine whether thereplication snapshot comprises the same data as the snapshot, thus thefirst storage and the second storage comprised the same data, which mayindicate that data was being correctly replicated from the first storageto the second storage). In an example, responsive to the snapshot andthe replication snapshot comprising different data, a determination maybe made that synchronous replication, between the first storagecontroller and the second storage controller based upon the synchronousreplication relationship, is not being performed correctly. In anotherexample, a dependent write order consistency of replication operationsto the second storage may be verified based upon the comparison of thesnapshot and the replication snapshot (e.g., if a write operation Adepends upon completion of a write operation B, then a replicated writeoperation B should be implemented by the second storage controllerbefore a replicated write operation A).

In an example, the snapshot may be an application consistent snapshotassociated with an application that utilizes the first storage (e.g., adatabase application) and the replication snapshot may be a replicationapplication consistent snapshot. For example, the application consistentsnapshot and the replication application consistent snapshot may becreated in response to a storage system replication module, integratedwithin the application, issuing a storage operating system API command,such as a ZAPI command, comprising the replication label as the snapshotcreate request. In particular, the application may be consulted todetermine a consistent point in time for the application (e.g., thedatabase may have little to no client access from midnight to 1:00 am).Accordingly, the snapshot create request, comprising the replicationlabel, may be sent based upon the consistent point in time.

The application consistent snapshot and/or the replication applicationconsistent snapshot may be used to quickly recover the application,previously using the first storage, to use the second storage in theevent the first storage controller fails or a failover command isreceived. Responsive to receiving the failover command or identifyingthe failure, a failover operation, from the first storage controller tothe second storage controller for providing clients with failover accessto replicated data within the second storage, may be performed. In anexample, the failover operation may be triggered within a thresholdamount of time (e.g., contemporaneously with) the creation of theapplication consistent snapshot and/or the replication applicationconsistent snapshot, which may mitigate data loss (e.g., improve arecovery time objective (RTO) to more quickly recover the application,which may be improved by trading off a recovery point objective (RPO)with some data loss, and such data loss may be mitigated by reducing thetime between the creation of the application consistent snapshot andtriggering failover) when using the application consistent snapshotand/or the replication application consistent snapshot for recoveringthe application. In this way, the replication application consistentsnapshot may be utilized to recover the application to utilize thesecond storage in place of the first storage. The application mayrecover more quickly because the replication application consistentsnapshot is used, and thus rolling forward, rolling backwards, and/orother recovery overhead processing may not be needed.

FIGS. 4A-4C illustrate examples of a system 400 for utilizing snapshotsfor data integrity validation. FIG. 4A illustrates a first storagecontroller 402, hosting first storage 408, having a synchronousreplication relationship 412 with a second storage controller 404hosting second storage 410 (e.g., a file, a LUN, a consistency group offiles or LUNs, a directory, and/or any other storage object may besynchronously replicated from the first storage 408 to the secondstorage 410 as replicated data). The first storage controller 402 may becapable of communicating with the second storage controller 404 over anetwork 406. The second storage controller 404 may be configured as adisaster recovery partner for the first storage controller 402, suchthat the second storage controller 404 may provide clients with failoveraccess to replicated data (e.g., data replicated from the first storage408 to the second storage 410) in the event the first storage controller402 fails.

A snapshot replication policy rule 414 may be defined for thesynchronous replication relationship 412. The snapshot replicationpolicy rule 414 may specify that a replication label (e.g. a string,such as “validation snapshot”) will be used to label snapshot createrequests, targeting the first storage 408, that are to be replicated tothe second storage 410. A snapshot creation policy 416 may be created toissue snapshot create requests with the replication label. In anexample, the snapshot creation policy 416 may be hosted on anapplication server, not illustrated, separate from the first storagecontroller 402.

FIG. 4B illustrates a snapshot create request 420 being created with thereplication label based upon the snapshot creation policy 416 (e.g., theapplication server may create and issue the snapshot create request 420to the first storage controller 402). The snapshot replication policyrule 414 may be used to evaluate the snapshot create request 420 todetermine that the snapshot create request 420 comprises the replicationlabel indicating that the snapshot create request 420 is to bereplicated to the second storage 410. Accordingly, the snapshot createrequest 420 may be locally implemented upon the first storage 408 tocreate a snapshot 422 comprising a point in time representation of datawithin the first storage 408. The snapshot create request 420 may bereplicated to the second storage controller 404 for creating areplication snapshot 424 comprising a point in time representation ofdata within the second storage 410.

FIG. 4C illustrates the snapshot 422 and the replication snapshot 424being compared 430 for data integrity validation and/or dependent writeorder consistency verification. In an example of data integrityvalidation, the snapshot 422 and the replication snapshot 424 may beevaluated to determine whether data of the first storage 408 and thesecond storage 410 was the same (e.g., synchronous replication wasworking correctly to replicate operations, targeting the first storage408, to the second storage 410) or different (e.g., the synchronousreplication was not working correctly, and thus troubleshooting may beperformed) when the snapshots were created. In an example of dependentwrite order consistency verification, the content of the snapshot 422and the replication snapshot 424 may be evaluated to determine whetherreplicated operations were being implemented upon the second storage 410is a correct order to preserve dependencies between operations.

FIGS. 5A-5C illustrate examples of a system 500 for utilizing snapshotsfor application recovery (e.g., application consistent snapshots, commonsnapshots, etc.). FIG. 5A illustrates a first storage controller 502,hosting first storage 508, having a synchronous replication relationship512 with a second storage controller 504 hosting second storage 510. Thefirst storage controller 502 may be capable of communicating with thesecond storage controller 504 over a network 506. The second storagecontroller 504 may be configured as a disaster recovery partner for thefirst storage controller 502, such that the second storage controller504 may provide clients with failover access to replicated data (e.g.,data replicated from the first storage 508 to the second storage 510) inthe event the first storage controller 502 fails. The first storagecontroller 502 may host an application 507, such as a databaseapplication, that utilizes the first storage 508. The application 507may be associated with an application aware plugin 509 that isconfigured to decide when an application consistent snapshot is to becreated by coordinating with the application 507 (e.g., snapshotscreated at application consistent points in time for the application507).

A snapshot replication policy rule 514 may be defined for thesynchronous replication relationship 512. The snapshot replicationpolicy rule 514 may specify that a replication label (e.g. a string,such as “app consistent snapshot”) will be used to label snapshot createrequests, targeting the first storage 508, that are to be replicated tothe second storage 510.

FIG. 5B illustrates a snapshot create request 520 being created with thereplication label by the application aware plugin 509. For example, theapplication 507 may be consulted to determine an application consistentpoint in time for the application 507 (e.g., a time period with littleto no client access to the database application). The snapshot createrequest 520 may be sent based upon the application consistent point intime so that snapshots of the first storage 508 and the second storage510 are created at application consistent points in time for theapplication 507. The snapshot create request 520 may be issued to thefirst storage controller 502 (e.g., a storage system replication module,integrated with the application 507, may issue a storage operatingsystem API command, such as a ZAPI command, comprising the replicationlabel as the snapshot create request 520). The snapshot replicationpolicy rule 514 may be used to evaluate the snapshot create request 520to determine that the snapshot create request 520 comprises thereplication label indicating that the snapshot create request 520 is tobe replicated to the second storage 510. Accordingly, the snapshotcreate request 520 may be locally implemented upon the first storage 508to create an application consistent snapshot 522 comprising a point intime representation of data within the first storage 508. The snapshotcreate request 520 may be replicated to the second storage controller504 for creating a replication application consistent snapshot 524comprising a point in time representation of data within the secondstorage 510.

FIG. 5C illustrates a failover operation 552 from the first storagecontroller 502 to the second storage controller 504 being performed. Inan example, the failover operation 552 may be performed in response to afailure 550 of the first storage controller 502. In another example, thefailover operation 552 may be a planned failover operation where astorage administrator is planning to shut down or restart the firststorage controller 502, and thus the failover operation 552 may beperformed within a threshold amount of time from the creation of theapplication consistent snapshot 522 and/or the replication applicationconsistent snapshot 524, which may mitigate data loss (e.g., and improvea recovery point objective (RPO)) otherwise occurring from operationsbeing implemented after the snapshots were created and before thefailover operation 552 is performed. In this way, the second storagecontroller 504 may takeover for the first storage controller 502 (e.g.,obtain access to the second storage 510 for providing clients withfailover access to replicated data, replicated from the first storage508 to the second storage 510, in place of the first storage controller502 providing primary access to original data within the first storage508). The replication application consistent snapshot 524 may be used toefficiently and quickly (e.g., without performing rollbacks, rollforwards, and/or other time and resource intensive tasks) recover 556the application 507 as a recovered application 554 that will utilize thesecond storage 510 in place of previously using the first storage 508(e.g., the database application may now use the second storage 510 formaintaining the database). In an example, files and/or LUNs may berestored back to a consistent snapshot before access is provided to theapplication 507.

Still another embodiment involves a computer-readable medium comprisingprocessor-executable instructions configured to implement one or more ofthe techniques presented herein. An example embodiment of acomputer-readable medium or a computer-readable device that is devisedin these ways is illustrated in FIG. 6 , wherein the implementation 600comprises a computer-readable medium 608, such as a CD-R, DVD-R, flashdrive, a platter of a hard disk drive, etc., on which is encodedcomputer-readable data 606. This computer-readable data 606, such asbinary data comprising at least one of a zero or a one, in turncomprises a processor-executable computer instructions 604 configured tooperate according to one or more of the principles set forth herein. Insome embodiments, the processor-executable computer instructions 604 areconfigured to perform a method 602, such as at least some of theexemplary method 300 of FIG. 3 , for example. In some embodiments, theprocessor-executable computer instructions 604 are configured toimplement a system, such as at least some of the exemplary system 400 ofFIGS. 4A-4C and/or at least some of the exemplary system 500 of FIGS.5A-5C, for example. Many such computer-readable media are contemplatedto operate in accordance with the techniques presented herein.

It will be appreciated that processes, architectures and/or proceduresdescribed herein can be implemented in hardware, firmware and/orsoftware. It will also be appreciated that the provisions set forthherein may apply to any type of special-purpose computer (e.g., filehost, storage server and/or storage serving appliance) and/orgeneral-purpose computer, including a standalone computer or portionthereof, embodied as or including a storage system. Moreover, theteachings herein can be configured to a variety of storage systemarchitectures including, but not limited to, a network-attached storageenvironment and/or a storage area network and disk assembly directlyattached to a client or host computer. Storage system should thereforebe taken broadly to include such arrangements in addition to anysubsystems configured to perform a storage function and associated withother equipment or systems.

In some embodiments, methods described and/or illustrated in thisdisclosure may be realized in whole or in part on computer-readablemedia. Computer readable media can include processor-executableinstructions configured to implement one or more of the methodspresented herein, and may include any mechanism for storing this datathat can be thereafter read by a computer system. Examples of computerreadable media include (hard) drives (e.g., accessible via networkattached storage (NAS)), Storage Area Networks (SAN), volatile andnon-volatile memory, such as read-only memory (ROM), random-accessmemory (RAM), EEPROM and/or flash memory, CD-ROMs, CD-Rs, CD-RWs, DVDs,cassettes, magnetic tape, magnetic disk storage, optical or non-opticaldata storage devices and/or any other medium which can be used to storedata.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter defined in the appended claims is not necessarilylimited to the specific features or acts described above. Rather, thespecific features and acts described above are disclosed as exampleforms of implementing at least some of the claims.

Various operations of embodiments are provided herein. The order inwhich some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated given the benefit ofthis description. Further, it will be understood that not all operationsare necessarily present in each embodiment provided herein. Also, itwill be understood that not all operations are necessary in someembodiments.

Furthermore, the claimed subject matter is implemented as a method,apparatus, or article of manufacture using standard application orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer application accessible from anycomputer-readable device, carrier, or media. Of course, manymodifications may be made to this configuration without departing fromthe scope or spirit of the claimed subject matter.

As used in this application, the terms “component”, “module,” “system”,“interface”, and the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware, software, or software in execution. For example, a componentincludes a process running on a processor, a processor, an object, anexecutable, a thread of execution, an application, or a computer. By wayof illustration, both an application running on a controller and thecontroller can be a component. One or more components residing within aprocess or thread of execution and a component may be localized on onecomputer or distributed between two or more computers.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication are generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Also, at least one of A and B and/or the like generally means A orB and/or both A and B. Furthermore, to the extent that “includes”,“having”, “has”, “with”, or variants thereof are used, such terms areintended to be inclusive in a manner similar to the term “comprising”.

Many modifications may be made to the instant disclosure withoutdeparting from the scope or spirit of the claimed subject matter. Unlessspecified otherwise, “first,” “second,” or the like are not intended toimply a temporal aspect, a spatial aspect, an ordering, etc. Rather,such terms are merely used as identifiers, names, etc. for features,elements, items, etc. For example, a first set of information and asecond set of information generally correspond to set of information Aand set of information B or two different or two identical sets ofinformation or the same set of information.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method, comprising: creating a snapshot offirst storage based upon a determination that a snapshot requestcomprises a replication label specified by a snapshot replication policyrule; creating a replication snapshot of second storage that ismaintained as a replication destination for the first storage; andcomparing the snapshot and the replication snapshot to determine whethersynchronous replication between a first controller hosting the firststorage and a second controller hosting the second storage is beingperformed correctly.
 2. The method of claim 1, comprising: performing adata integrity validation upon the snapshot and the replication snapshotto determine that data is being correctly replicated by the synchronousreplication from the first storage to the second storage based upon thesnapshot and the replication snapshot comprising the same data.
 3. Themethod of claim 1, comprising: performing a data integrity validationupon the snapshot and the replication snapshot to determine that data isnot being correctly replicated by the synchronous replication from thefirst storage to the second storage based upon the snapshot and thereplication snapshot comprising different data.
 4. The method of claim1, comprising: determining a dependent write order corresponding to anorder with which operations, executed upon the first storage, aredependent upon one another; and verifying whether a dependent writeorder consistency of replication operations to the second storage hasbeen maintained based upon whether the replication operations areexecuted upon the second storage according to the order with whichcorresponding operations were executed upon the first storage accordingto the dependent write order.
 5. The method of claim 1, comprising:receiving an operation, targeting a storage object within the firststorage, from a client; responsive to determining that a synchronousreplication relationship applies to the storage object, replicating theoperation as a replication operation that is a replica of the operation;locally implementing the operation upon the storage object; sending thereplication operation to the second controller for remote implementationupon a replicated storage object within the second storage, thereplicated storage object corresponding to a backup replication of thestorage object; and responsive to the operation and the replicationoperation completing, acknowledging back to the client.
 6. The method ofclaim 5, wherein the locally implementing comprises: completing pendingoperations targeting the storage object before locally implementing theoperation.
 7. The method of claim 5, wherein the locally implementingcomprises: receiving a new operation, targeting the storage object,while locally implementing the operation; queueing the new operationinto a queue as a queued operation; and responsive to locallyimplementing the operation, dequeuing and implementing the queuedoperation.
 8. The method of claim 1, comprising: identifying a failureof a first storage controller hosting the first storage; performing aswitchover operation from the first storage controller to a secondstorage controller hosting the second storage for providing clients withfailover access to replicated data within the second storage; andutilizing the replication snapshot to recover an application to utilizethe second storage in place of the first storage.
 9. The method of claim1, comprising: receiving a switchover command to switchover from a firststorage controller hosting the first storage to a second storagecontroller hosting the second storage; performing a switchover operationfrom the first storage controller to the second storage controller forproviding clients with failover access to replicated data within thesecond storage based upon the switchover command; and utilizing thereplication snapshot to recover an application to utilize the secondstorage in place of the first storage.
 10. A non-transitory machinereadable medium having stored thereon machine executable code which whenexecuted by a machine, causes the machine to: receive an operation,targeting a storage object within first storage, from a client;responsive to determining that a synchronous replication relationshipbetween a first controller hosting the first storage and a secondcontroller hosting second storage applies to the storage object, splitthe operation into a replication operation; locally implement theoperation upon the storage object; send the replication operation to thesecond controller for remote implementation upon a replicated storageobject within the second storage, the replicated storage objectcorresponding to a backup replication of the storage object; responsiveto the operation and the replication operation completing, acknowledgeback to the client; and creating a snapshot of the first storage basedupon a determination that a snapshot request comprises a replicationlabel specified by a snapshot replication policy rule.
 11. Thenon-transitory machine readable medium of claim 10, wherein the machineexecutable code causes the machine to: complete pending operationstargeting the storage object before locally implementing the operation.12. The non-transitory machine readable medium of claim 10, wherein themachine executable code causes the machine to: receive a new operation,targeting the storage object, while locally implementing the operation;queue the new operation into a queue as a queued operation; andresponsive to locally implementing the operation, dequeue and implementthe queued operation.
 13. The non-transitory machine readable medium ofclaim 10, wherein the machine executable code causes the machine to: inresponse to the synchronous replication not working correctly, implementa troubleshooting action.
 14. The non-transitory machine readable mediumof claim 10, wherein the machine executable code causes the machine to:determine that the synchronous replication is being performedincorrectly based upon the snapshot of the first storage and areplication snapshot of the second storage comprising different data.15. The non-transitory machine readable medium of claim 10, wherein themachine executable code causes the machine to: identify a failure of afirst storage controller hosting the first storage; perform a switchoveroperation from the first storage controller to a second storagecontroller hosting the second storage for providing clients withfailover access to replicated data within the second storage; andutilize a replication snapshot to recover an application to utilize thesecond storage in place of the first storage.
 16. The non-transitorymachine readable medium of claim 10, wherein the machine executable codecauses the machine to: receive a switchover command to switchover from afirst storage controller hosting the first storage to a second storagecontroller hosting the second storage; perform a switchover operationfrom the first storage controller to the second storage controller forproviding clients with failover access to replicated data within thesecond storage based upon the switchover command; and utilize areplication snapshot to recover an application to utilize the secondstorage in place of the first storage.
 17. A computing devicecomprising: a memory containing machine readable medium comprisingmachine executable code having stored thereon instructions forperforming a method; and a processor coupled to the memory, theprocessor configured to execute the machine executable code to cause theprocessor to: create a snapshot of first storage based upon adetermination that a snapshot request comprises a replication labelspecified by a snapshot replication policy rule; create a replicationsnapshot of second storage that is maintained as a replicationdestination for the first storage; compare the snapshot and thereplication snapshot to determine whether synchronous replicationbetween a first controller hosting the first storage and a secondcontroller hosting the second storage is being performed correctly; andin response to the synchronous replication not working correctly,implement a troubleshooting action.
 18. The computing device of claim17, and wherein the machine executable code causes the processor to:perform a data integrity validation upon the snapshot and thereplication snapshot to determine that data is being correctlyreplicated by the synchronous replication from the first storage to thesecond storage based upon the snapshot and the replication snapshotcomprising the same data.
 19. The computing device of claim 17, andwherein the machine executable code causes the processor to: perform adata integrity validation upon the snapshot and the replication snapshotto determine that data is not being correctly replicated by thesynchronous replication from the first storage to the second storagebased upon the snapshot and the replication snapshot comprisingdifferent data.
 20. The computing device of claim 17, and wherein themachine executable code causes the processor to: receive an operation,targeting a storage object within the first storage, from a client;responsive to determining that a synchronous replication relationshipapplies to the storage object, split the operation into a replicationoperation; locally implement the operation upon the storage object; sendthe replication operation to the second controller for remoteimplementation upon a replicated storage object within the secondstorage, the replicated storage object corresponding to a backupreplication of the storage object; and responsive to the operation andthe replication operation completing, acknowledge back to the client.